1 00:00:04,120 --> 00:00:07,160 Speaker 1: Get in touch with technology with tech Stuff from how 2 00:00:07,200 --> 00:00:14,000 Speaker 1: stuff works dot com. Hey there, and welcome to tech Stuff. 3 00:00:14,040 --> 00:00:17,760 Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer with 4 00:00:17,880 --> 00:00:20,000 Speaker 1: How Stuff Works, and I heart radio and I love 5 00:00:20,079 --> 00:00:23,320 Speaker 1: all things tech. And you know, we've been going pretty 6 00:00:23,360 --> 00:00:27,200 Speaker 1: fast with tech stuff over the past I don't know, decade, 7 00:00:27,840 --> 00:00:31,159 Speaker 1: So I felt maybe it was time to apply the 8 00:00:31,320 --> 00:00:34,800 Speaker 1: brakes a little bit. I don't mean to slow down 9 00:00:34,840 --> 00:00:37,880 Speaker 1: the show or stop it, but rather to take time 10 00:00:37,920 --> 00:00:41,280 Speaker 1: to talk about how breaks work and the science surrounding breaks, 11 00:00:41,960 --> 00:00:46,040 Speaker 1: because puns are sort of a thing I do, but seriously, 12 00:00:46,280 --> 00:00:47,840 Speaker 1: I thought this would give us a chance to talk 13 00:00:47,880 --> 00:00:51,440 Speaker 1: about mechanical and hydraulic systems as well as the science 14 00:00:52,000 --> 00:00:57,600 Speaker 1: that's behind breaking, the physics that are involved. So first, 15 00:00:57,920 --> 00:01:00,640 Speaker 1: let's talk about what makes breaks no necessary in the 16 00:01:00,640 --> 00:01:03,600 Speaker 1: first place, which is pretty obvious stuff, but it leads 17 00:01:03,720 --> 00:01:07,800 Speaker 1: into a discussion about physical forces that guided the whole 18 00:01:07,800 --> 00:01:13,840 Speaker 1: evolution of breaks. So, a body in motion has momentum. 19 00:01:14,080 --> 00:01:18,120 Speaker 1: Momentum is a quantity of movement. It depends upon two things, 20 00:01:18,600 --> 00:01:22,080 Speaker 1: the mass of the object that's in motion and how 21 00:01:22,160 --> 00:01:25,840 Speaker 1: quickly that mass is moving. So really comes down to 22 00:01:25,920 --> 00:01:29,039 Speaker 1: how much of the stuff is there and how fast 23 00:01:29,200 --> 00:01:33,039 Speaker 1: is it going. A simple equation would be momentum equals 24 00:01:33,480 --> 00:01:38,039 Speaker 1: mass times velocity. So if you have something with a 25 00:01:38,200 --> 00:01:41,920 Speaker 1: low mass, like a bullet, but it's traveling at a 26 00:01:42,040 --> 00:01:45,240 Speaker 1: high velocity, it has a pretty good amount of momentum. 27 00:01:45,560 --> 00:01:49,240 Speaker 1: If you have something that's really really huge, like a glacier, 28 00:01:49,440 --> 00:01:53,360 Speaker 1: but it's moving incredibly slowly, it still has a lot 29 00:01:53,360 --> 00:01:57,280 Speaker 1: of momentum, because momentum depends upon both the mass and 30 00:01:57,320 --> 00:01:59,680 Speaker 1: the velocity, not just one or the other. Now, if 31 00:01:59,680 --> 00:02:02,160 Speaker 1: you have something that's of a pretty decent size, like 32 00:02:02,200 --> 00:02:04,840 Speaker 1: a vehicle, and it's moving at a pretty good speed, 33 00:02:05,480 --> 00:02:08,800 Speaker 1: then that has got a lot of momentum too. And 34 00:02:09,120 --> 00:02:13,120 Speaker 1: that's a problem, right If you've got a mass that's 35 00:02:13,120 --> 00:02:15,720 Speaker 1: moving at a pretty good speed and you need to 36 00:02:15,760 --> 00:02:18,320 Speaker 1: stop that mass, you have to figure out how do 37 00:02:18,360 --> 00:02:22,280 Speaker 1: you offset that momentum, How do you convert this movement 38 00:02:22,400 --> 00:02:26,480 Speaker 1: energy into something else. So momentum is also a vector 39 00:02:26,560 --> 00:02:31,200 Speaker 1: quantity vectors and physics have not just a magnitude but 40 00:02:31,400 --> 00:02:36,160 Speaker 1: also a direction. Acceleration is the same. It has a 41 00:02:36,160 --> 00:02:39,800 Speaker 1: magnitude and a direction. So to fully describe momentum, we 42 00:02:39,840 --> 00:02:43,000 Speaker 1: need not just how many kilograms of mass are traveling 43 00:02:43,000 --> 00:02:46,320 Speaker 1: at a speed typically in meters per second, but also 44 00:02:46,360 --> 00:02:49,880 Speaker 1: the direction of travel. Now, a body and motion has 45 00:02:49,960 --> 00:02:54,080 Speaker 1: kinetic energy as well. So to reduce momentum and stop 46 00:02:54,160 --> 00:02:57,760 Speaker 1: a body in motion, you need to convert that kinetic energy, 47 00:02:57,840 --> 00:03:02,160 Speaker 1: that energy of movement in to something else. Because we 48 00:03:02,200 --> 00:03:06,200 Speaker 1: have to remember the laws of conservation, the laws of 49 00:03:06,200 --> 00:03:09,320 Speaker 1: the universe. We we energy cannot be created, it cannot 50 00:03:09,360 --> 00:03:13,280 Speaker 1: be destroyed. We cannot just make energy, we cannot destroy energy. 51 00:03:13,320 --> 00:03:17,440 Speaker 1: We can convert it from one form into another. So 52 00:03:17,560 --> 00:03:21,359 Speaker 1: breaks do this by converting the kinetic energy of an 53 00:03:21,400 --> 00:03:26,720 Speaker 1: object in motion into heat through friction. And you've probably 54 00:03:26,800 --> 00:03:30,040 Speaker 1: heard the term waste heat. Now what we mean by 55 00:03:30,080 --> 00:03:32,480 Speaker 1: that is that we've got some sort of system. It 56 00:03:32,520 --> 00:03:36,240 Speaker 1: can be pretty much any given mechanical system in particular, 57 00:03:36,280 --> 00:03:40,520 Speaker 1: but really other systems as well, biological systems. Uh So, 58 00:03:40,560 --> 00:03:44,040 Speaker 1: it could be pretty much anything. And in this system, 59 00:03:44,240 --> 00:03:47,600 Speaker 1: some of the energy that we're depending on is going 60 00:03:47,680 --> 00:03:49,920 Speaker 1: not to whatever it is we're trying to do, but 61 00:03:50,120 --> 00:03:53,800 Speaker 1: rather into generating heat. So with a bicycle, some of 62 00:03:53,800 --> 00:03:57,840 Speaker 1: the energy we're putting forth by peddling is not going 63 00:03:57,880 --> 00:04:00,840 Speaker 1: directly to making us move we're losing it in the 64 00:04:00,880 --> 00:04:04,800 Speaker 1: form of friction, and thus heat um really the heat 65 00:04:04,840 --> 00:04:07,760 Speaker 1: that's generated from friction. That's the best way of putting it. 66 00:04:08,160 --> 00:04:11,440 Speaker 1: The heat represents energy that we could not otherwise exploit 67 00:04:11,600 --> 00:04:13,760 Speaker 1: for whatever it is we're trying to do. So here's 68 00:04:13,800 --> 00:04:17,279 Speaker 1: another example, with an electrical generator. We might say that 69 00:04:17,320 --> 00:04:21,280 Speaker 1: the friction of the moving parts inside that electrical generator 70 00:04:21,600 --> 00:04:24,720 Speaker 1: means that some of the kinetic energy we would otherwise 71 00:04:24,839 --> 00:04:28,440 Speaker 1: use to create more electricity is instead converting to heat, 72 00:04:28,960 --> 00:04:32,200 Speaker 1: and that heat isn't being captured in any meaningful way. 73 00:04:32,279 --> 00:04:37,159 Speaker 1: So the work we did two direct this kinetic energy 74 00:04:37,240 --> 00:04:40,920 Speaker 1: to the generator was wasted. Some of that work we 75 00:04:40,920 --> 00:04:44,880 Speaker 1: weren't able to get efficiency. So no system is perfect. 76 00:04:45,040 --> 00:04:47,760 Speaker 1: Any system with moving parts is going to have friction 77 00:04:47,839 --> 00:04:50,040 Speaker 1: to deal with. And there are a lot of super 78 00:04:50,040 --> 00:04:53,279 Speaker 1: smart materials scientists out there who have worked really hard 79 00:04:53,680 --> 00:04:57,080 Speaker 1: to develop stuff that generates very little friction, and that 80 00:04:57,279 --> 00:05:00,240 Speaker 1: is in an effort to increase efficiency and minim eyes 81 00:05:00,279 --> 00:05:03,360 Speaker 1: waist heat. But when it comes to breaks, we want 82 00:05:03,440 --> 00:05:07,280 Speaker 1: that friction. That's what is stopping an object. So we 83 00:05:07,360 --> 00:05:11,640 Speaker 1: need something that is really good at creating this friction. 84 00:05:11,680 --> 00:05:14,400 Speaker 1: We want to convert that kinetic energy into heat and 85 00:05:14,440 --> 00:05:18,720 Speaker 1: thus decrease the momentum of a fast moving massive object, 86 00:05:19,040 --> 00:05:21,479 Speaker 1: perhaps even bringing that object to a complete stop, not 87 00:05:21,600 --> 00:05:24,200 Speaker 1: just slowing it down, but stopping it. So in the 88 00:05:24,320 --> 00:05:29,480 Speaker 1: very early days of break systems, even before there were cars, 89 00:05:30,040 --> 00:05:33,200 Speaker 1: you were looking at a pretty simple device. And this 90 00:05:33,240 --> 00:05:36,000 Speaker 1: would be in the horse drawn carriage era. You've got 91 00:05:36,040 --> 00:05:39,599 Speaker 1: a carriage that's being pulled by horses. Even when the 92 00:05:39,600 --> 00:05:41,920 Speaker 1: horses start to slow down, you know you still have 93 00:05:42,000 --> 00:05:44,640 Speaker 1: the momentum of the actual carriage itself. You need to 94 00:05:44,680 --> 00:05:48,599 Speaker 1: slow down the carriage uh to to come to a stop. 95 00:05:48,640 --> 00:05:52,400 Speaker 1: So the break was typically a lever, and the long 96 00:05:52,520 --> 00:05:55,400 Speaker 1: end of the lever was extended up towards the driver. 97 00:05:55,520 --> 00:05:57,720 Speaker 1: That was the handle side, So the longside of the 98 00:05:57,800 --> 00:05:59,800 Speaker 1: lever is the handle. On the short end of the 99 00:06:00,000 --> 00:06:04,640 Speaker 1: ever was a wooden block. The wooden block was when 100 00:06:04,680 --> 00:06:07,800 Speaker 1: you pull, the lever, would make contact, typically with the 101 00:06:07,880 --> 00:06:11,640 Speaker 1: driver's side front wheel of the carriage to create that 102 00:06:11,720 --> 00:06:14,599 Speaker 1: source of friction and convert the kinetic energy of the 103 00:06:14,640 --> 00:06:18,600 Speaker 1: turning wheel into heat and thus slow and eventually stop 104 00:06:18,760 --> 00:06:22,479 Speaker 1: the carriage. A lever is one of the classic simple 105 00:06:22,600 --> 00:06:26,279 Speaker 1: machines it's a bar that rotates around the fulcrum, and 106 00:06:26,320 --> 00:06:29,200 Speaker 1: a fulcrum is just a fixed point. So the length 107 00:06:29,279 --> 00:06:32,880 Speaker 1: of the lever on either side of the fulcrum determines 108 00:06:32,960 --> 00:06:36,000 Speaker 1: the amount of effort or force exerted or acquired per side. 109 00:06:36,360 --> 00:06:40,640 Speaker 1: In a classic class one lever, lever makes certain types 110 00:06:40,680 --> 00:06:43,479 Speaker 1: of work, such as lifting, easier by reducing the workload 111 00:06:43,880 --> 00:06:47,159 Speaker 1: that is needed to affect a change to to create 112 00:06:47,200 --> 00:06:51,000 Speaker 1: that lift. There are three classes of levers, and I 113 00:06:51,080 --> 00:06:53,840 Speaker 1: just mentioned class one lever. That's the one where you've 114 00:06:53,880 --> 00:06:56,920 Speaker 1: got a force that's applied on one end of the lever, 115 00:06:57,760 --> 00:07:00,400 Speaker 1: you have a load the thing you're trying to move 116 00:07:00,720 --> 00:07:03,680 Speaker 1: or activate on the other end of the lever, and 117 00:07:03,760 --> 00:07:07,680 Speaker 1: the fulcrum is somewhere in between those two. If it's 118 00:07:07,680 --> 00:07:11,200 Speaker 1: in the center of the bar, then the fulcrum ends 119 00:07:11,280 --> 00:07:14,280 Speaker 1: up balancing loads on either side. If you put equal 120 00:07:14,360 --> 00:07:17,280 Speaker 1: loads on either side, it should just balance out, kind 121 00:07:17,280 --> 00:07:19,320 Speaker 1: of like you know, just a scale if you think 122 00:07:19,320 --> 00:07:21,320 Speaker 1: of it that way. So a see saw or a 123 00:07:21,320 --> 00:07:24,280 Speaker 1: teeter totter would be an example of a class one lever. 124 00:07:25,160 --> 00:07:26,960 Speaker 1: If two people weigh the same on a seesaw, it 125 00:07:26,960 --> 00:07:29,320 Speaker 1: balances out. But if you put a heavier person on 126 00:07:29,320 --> 00:07:31,320 Speaker 1: one end and a lighter person on the other. The 127 00:07:31,320 --> 00:07:33,840 Speaker 1: heavier person sinks down the lighter person goes up into 128 00:07:34,120 --> 00:07:37,560 Speaker 1: the air. But if the heavier person were to scoot 129 00:07:37,720 --> 00:07:42,560 Speaker 1: forward on the seesaw to decrease the space between the 130 00:07:42,560 --> 00:07:46,360 Speaker 1: heavier person and the fulcrumb, then you would eventually balance out. 131 00:07:46,400 --> 00:07:49,800 Speaker 1: And if the heavier person kept scooting forward to get 132 00:07:49,800 --> 00:07:53,120 Speaker 1: closer to the fulcrum, the lighter person would eventually sink 133 00:07:53,200 --> 00:07:55,160 Speaker 1: to the bottom and the heavier person would be up 134 00:07:55,160 --> 00:08:01,360 Speaker 1: in the air. So by decreasing the disc dins between 135 00:08:01,440 --> 00:08:06,160 Speaker 1: the load and the fulcrum, you can increase the the 136 00:08:06,200 --> 00:08:09,880 Speaker 1: lifting power essentially, or the really you're decreasing the amount 137 00:08:09,880 --> 00:08:12,320 Speaker 1: of force needed to lift that load, if you're really 138 00:08:12,320 --> 00:08:15,080 Speaker 1: thinking about it that way, you're creating a mechanical advantage. 139 00:08:16,000 --> 00:08:18,160 Speaker 1: But there are two other classes of levers. I should 140 00:08:18,160 --> 00:08:22,240 Speaker 1: probably cover those because some of them actually factor into 141 00:08:22,280 --> 00:08:25,800 Speaker 1: breaks as well later down the line. Class two levers 142 00:08:26,160 --> 00:08:29,520 Speaker 1: put the fulcrum on one end of a bar, so 143 00:08:29,720 --> 00:08:32,000 Speaker 1: instead of it being in the middle, somewhere the fulcrum 144 00:08:32,080 --> 00:08:34,120 Speaker 1: the fixed point is actually on one end of the bar. 145 00:08:34,600 --> 00:08:36,400 Speaker 1: The load is somewhere in the middle of the bar 146 00:08:36,720 --> 00:08:39,040 Speaker 1: and the force is at the far into the bar. 147 00:08:39,720 --> 00:08:42,880 Speaker 1: So a wheelbarrow is this type of lever, because these 148 00:08:42,920 --> 00:08:45,600 Speaker 1: can be kind of difficult to imagine otherwise. But if 149 00:08:45,600 --> 00:08:49,839 Speaker 1: you think about the wheel on a wheelbarrow is a fulcrum, 150 00:08:49,920 --> 00:08:52,960 Speaker 1: and you put a load of stuff into the wheelbarrow itself, 151 00:08:53,520 --> 00:08:55,559 Speaker 1: and then you lift the other side of the wheelbarrow 152 00:08:55,600 --> 00:08:57,920 Speaker 1: by the handles. So the closer the load is to 153 00:08:57,960 --> 00:09:00,679 Speaker 1: the fulcrum, the more the mechanical advantage you will have 154 00:09:01,360 --> 00:09:04,400 Speaker 1: uh and the less you will the less effort you'll 155 00:09:04,440 --> 00:09:08,000 Speaker 1: need to lift the handles for a given load. Or 156 00:09:08,480 --> 00:09:10,560 Speaker 1: you can think of it another way, the heavier the 157 00:09:10,600 --> 00:09:12,800 Speaker 1: load you will be able to manage as long as 158 00:09:12,840 --> 00:09:16,120 Speaker 1: it's closer to the fulcrum. A class three lever has 159 00:09:16,160 --> 00:09:19,480 Speaker 1: the fulcrum on one end, the load at the other end, 160 00:09:19,720 --> 00:09:22,160 Speaker 1: and the lifting force is in the middle. Now, these 161 00:09:22,240 --> 00:09:25,760 Speaker 1: leavers don't provide mechanical advantage, but they can increase the 162 00:09:25,800 --> 00:09:29,600 Speaker 1: speed at which a force moves a load. A baseball 163 00:09:29,640 --> 00:09:32,000 Speaker 1: bat would be an example of this, or even your 164 00:09:32,240 --> 00:09:34,200 Speaker 1: your own forearm would be an example of this. But 165 00:09:34,240 --> 00:09:37,439 Speaker 1: we're gonna leave the off from here because class three 166 00:09:37,520 --> 00:09:41,800 Speaker 1: leavers don't really factor into the discussion for breaking, So 167 00:09:41,840 --> 00:09:44,280 Speaker 1: the wooden block break is a Class one lever. On 168 00:09:44,280 --> 00:09:46,720 Speaker 1: one end is the wooden block, its position near the 169 00:09:46,760 --> 00:09:49,520 Speaker 1: carriage wheel. A little bit further up from the wooden 170 00:09:49,520 --> 00:09:53,319 Speaker 1: block is the fulcrum, the fixed point closer to the 171 00:09:53,320 --> 00:09:56,200 Speaker 1: wooden block than to the handle, and the other end 172 00:09:56,200 --> 00:09:58,680 Speaker 1: of the lever, the long end has the handle, so 173 00:09:58,760 --> 00:10:01,600 Speaker 1: the handle must travel a radar distance than the wooden block. 174 00:10:02,000 --> 00:10:04,600 Speaker 1: When you pull back on the brake um, you are 175 00:10:04,640 --> 00:10:08,920 Speaker 1: pulling the breakback much further than the wooden block has 176 00:10:08,960 --> 00:10:12,240 Speaker 1: to travel to make contact with the the carriage wheel. 177 00:10:12,960 --> 00:10:15,559 Speaker 1: But by increasing that distance, you reduce the amount of 178 00:10:15,600 --> 00:10:17,920 Speaker 1: work you need to do on the force end to 179 00:10:17,960 --> 00:10:20,760 Speaker 1: get a result on the load end. Uh. This is 180 00:10:20,800 --> 00:10:23,680 Speaker 1: important because if you're going pretty fast and you need 181 00:10:23,720 --> 00:10:26,520 Speaker 1: to slow down that wheel, you need to exert a 182 00:10:26,559 --> 00:10:29,920 Speaker 1: good deal of force to create enough friction and convert 183 00:10:29,960 --> 00:10:34,120 Speaker 1: that kinetic energy into heat. You couldn't easily do that 184 00:10:34,200 --> 00:10:36,679 Speaker 1: if you were, let's say, just holding a wooden block 185 00:10:37,240 --> 00:10:40,559 Speaker 1: and just trying to push the wooden block directly against 186 00:10:40,640 --> 00:10:43,240 Speaker 1: the carriage wheel. You probably wouldn't be able to do 187 00:10:43,280 --> 00:10:46,360 Speaker 1: that with enough force. To make a difference in a 188 00:10:46,360 --> 00:10:48,640 Speaker 1: sufficient amount of time. By putting it on this lever, 189 00:10:49,160 --> 00:10:52,080 Speaker 1: you can increase the amount of force you're exerting on 190 00:10:52,160 --> 00:10:56,400 Speaker 1: the wheel itself on the carriage wheel through pressure with 191 00:10:56,480 --> 00:10:58,480 Speaker 1: this wooden block, then you would if you were to 192 00:10:58,480 --> 00:11:01,520 Speaker 1: do it directly. So the lever makes the job easier. 193 00:11:02,720 --> 00:11:07,720 Speaker 1: Very important part of physics in general. The brake system 194 00:11:07,760 --> 00:11:10,800 Speaker 1: made the transition from horse drawn carriages to some of 195 00:11:10,840 --> 00:11:13,440 Speaker 1: the earliest automobiles in the nineteenth century, and it was 196 00:11:13,800 --> 00:11:15,880 Speaker 1: the same sort of thing. They were using wooden blocks. 197 00:11:16,240 --> 00:11:20,640 Speaker 1: The wheels on these early automobiles were often metal. There 198 00:11:20,960 --> 00:11:25,200 Speaker 1: was no rubber tires yet, and they worked reasonably well 199 00:11:25,360 --> 00:11:28,840 Speaker 1: under certain conditions, namely that the vehicles were traveling at 200 00:11:28,880 --> 00:11:31,920 Speaker 1: slower speeds were talking below twenty miles per hour or 201 00:11:31,960 --> 00:11:36,480 Speaker 1: below thirty two kilometers per hour, and traffic was pretty 202 00:11:36,600 --> 00:11:39,240 Speaker 1: light in those days, so there weren't a lot of 203 00:11:40,000 --> 00:11:42,600 Speaker 1: incidents where you would need to break quickly due to 204 00:11:42,920 --> 00:11:46,560 Speaker 1: an increased amount of traffic on the streets. But you 205 00:11:46,600 --> 00:11:50,320 Speaker 1: also weren't necessarily uh, it wasn't necessarily a good idea 206 00:11:50,360 --> 00:11:53,240 Speaker 1: to go, like driving a car up a steep hill, 207 00:11:53,360 --> 00:11:57,920 Speaker 1: for example, because your breaking system was pretty primitive. The 208 00:11:57,960 --> 00:12:00,120 Speaker 1: only way you would prevent yourself from rolling backwards was 209 00:12:00,120 --> 00:12:05,280 Speaker 1: either by applying more acceleration to overcome the force of 210 00:12:05,320 --> 00:12:09,240 Speaker 1: gravity that's pulling you down, or to hold a break 211 00:12:09,840 --> 00:12:15,120 Speaker 1: real strong against that wheel so that you're not slipping backward. Uh. 212 00:12:15,160 --> 00:12:18,319 Speaker 1: This also was probably a good thing. Like that, It's 213 00:12:18,320 --> 00:12:20,720 Speaker 1: probably a good thing you weren't going very fast, not 214 00:12:20,840 --> 00:12:24,960 Speaker 1: just because the brakes were primitive, but because those wheels 215 00:12:25,000 --> 00:12:27,760 Speaker 1: were metal. You would feel it when you would run 216 00:12:27,840 --> 00:12:30,440 Speaker 1: over bumps in the road, of which there were many. 217 00:12:31,000 --> 00:12:33,680 Speaker 1: It was very similar to if you remember my episodes 218 00:12:33,720 --> 00:12:37,280 Speaker 1: about the history of the bicycle, the bone shaker, that 219 00:12:37,280 --> 00:12:40,360 Speaker 1: it was a nickname for a type of early bicycle 220 00:12:40,520 --> 00:12:44,640 Speaker 1: that was really uncomfortable to ride. It was a very uh, 221 00:12:44,840 --> 00:12:48,520 Speaker 1: stiff ride, you might say. But it was clear the 222 00:12:48,600 --> 00:12:53,520 Speaker 1: lever approach wasn't going to remain sufficient as cars were 223 00:12:53,520 --> 00:12:56,960 Speaker 1: getting faster and heavier and traffic was increasing. You could 224 00:12:56,960 --> 00:12:59,520 Speaker 1: stop a faster car with a lever breake, but it 225 00:12:59,520 --> 00:13:03,200 Speaker 1: would take longer as you converted that kinetic energy into 226 00:13:03,200 --> 00:13:07,560 Speaker 1: heat through friction, so you didn't come to a stop 227 00:13:07,679 --> 00:13:11,040 Speaker 1: in as reasonable amount of space. You know, and an 228 00:13:11,080 --> 00:13:13,480 Speaker 1: increase in traffic, you had a decreased the email of 229 00:13:13,520 --> 00:13:17,320 Speaker 1: time you had in order to slow down to avoid collisions. 230 00:13:17,360 --> 00:13:20,040 Speaker 1: So something had to change. A couple of people came 231 00:13:20,120 --> 00:13:25,280 Speaker 1: up with some very clever alternatives. One was a proposal 232 00:13:25,440 --> 00:13:29,200 Speaker 1: that was made. It was actually not just proposed, it 233 00:13:29,240 --> 00:13:33,320 Speaker 1: was developed. It was the creation of Elmer Ambrose Sperry 234 00:13:33,520 --> 00:13:38,840 Speaker 1: of Cleveland, Ohio. Sperry's solution involved using disc brakes. Now 235 00:13:38,840 --> 00:13:41,360 Speaker 1: I'm going to cover modern disc brakes a little later 236 00:13:41,360 --> 00:13:44,000 Speaker 1: in this episode, but it's good to just go ahead 237 00:13:44,040 --> 00:13:46,800 Speaker 1: and then explain what the general idea was because it 238 00:13:46,840 --> 00:13:51,000 Speaker 1: remained the same even later on. So let's say you've 239 00:13:51,040 --> 00:13:53,360 Speaker 1: got a wheel, and you've got that hub of the wheel. 240 00:13:53,440 --> 00:13:57,200 Speaker 1: This is part that turns on the axle. Attached to that, 241 00:13:57,520 --> 00:14:01,400 Speaker 1: you have a disk that is really just part of 242 00:14:01,440 --> 00:14:04,200 Speaker 1: the hub of the wheel, but it's separate from the tire. 243 00:14:04,640 --> 00:14:08,760 Speaker 1: So you've got this free standing disc. Positioned over this 244 00:14:08,800 --> 00:14:12,120 Speaker 1: disc is a set of calipers, so that either side 245 00:14:12,160 --> 00:14:15,120 Speaker 1: of the caliper are on either side of the disk, 246 00:14:15,480 --> 00:14:18,200 Speaker 1: and it can pinch down on the disk, just like 247 00:14:18,280 --> 00:14:21,880 Speaker 1: your fingers would pinch down if you had let's say 248 00:14:21,920 --> 00:14:26,640 Speaker 1: a spinning frisbee between two fingers and you rut uh. 249 00:14:26,680 --> 00:14:29,040 Speaker 1: You know, your friend is holding their two fingers together, 250 00:14:29,600 --> 00:14:32,040 Speaker 1: and the frisbee is spinning around on the axle of 251 00:14:32,040 --> 00:14:35,120 Speaker 1: those two fingers. If you brought your fingers like calipers, 252 00:14:35,200 --> 00:14:37,600 Speaker 1: right on the gadge and then pinched, you could stop 253 00:14:37,600 --> 00:14:40,920 Speaker 1: the frisbee and its spin. That's the same idea as 254 00:14:41,000 --> 00:14:46,440 Speaker 1: this set of disc brakes the the In a sense, 255 00:14:46,440 --> 00:14:48,480 Speaker 1: it's working very similar to the way the wooden block 256 00:14:48,600 --> 00:14:51,440 Speaker 1: that would press directly against the wheel itself works, except 257 00:14:51,480 --> 00:14:54,880 Speaker 1: instead of of hitting the wheel, you're hitting this disc 258 00:14:54,960 --> 00:14:59,200 Speaker 1: that's attached to the wheel. Um. Pretty clever. And Sperry 259 00:14:59,360 --> 00:15:02,880 Speaker 1: was working on an early electric vehicle. You may remember 260 00:15:02,920 --> 00:15:05,000 Speaker 1: in some of my previous episodes, I've talked about how 261 00:15:05,080 --> 00:15:10,520 Speaker 1: electric cars actually pre date internal combustion engine cars. The 262 00:15:10,600 --> 00:15:16,280 Speaker 1: earliest automobiles were electric vehicles, not not gasoline powered vehicles. 263 00:15:16,320 --> 00:15:18,560 Speaker 1: So he's working on this electric car, and he was 264 00:15:18,600 --> 00:15:23,240 Speaker 1: actually using electro magnetism to close those calipers, to shut them, 265 00:15:23,880 --> 00:15:26,320 Speaker 1: to attract the pincher to the disk and have it 266 00:15:26,760 --> 00:15:31,640 Speaker 1: clamped tight enough to start to break the wheel. Uh. 267 00:15:31,960 --> 00:15:36,680 Speaker 1: Springs that were attached to the calipers would create the 268 00:15:36,680 --> 00:15:39,240 Speaker 1: force that would allow the calipers to open up again 269 00:15:39,280 --> 00:15:41,840 Speaker 1: once the electro magnetic field went away. So if you 270 00:15:41,880 --> 00:15:45,160 Speaker 1: were to step on a brake in Sperry's design, you 271 00:15:45,200 --> 00:15:48,640 Speaker 1: would cause a current to flow through the braking system, 272 00:15:48,640 --> 00:15:52,920 Speaker 1: thus generating the electromagnetic field and forcing the calipers closed 273 00:15:53,440 --> 00:15:57,280 Speaker 1: and breaking the disk, breaking b R A K I, 274 00:15:57,520 --> 00:16:02,080 Speaker 1: n G. The disk. Letting the foot pedal brake would 275 00:16:02,080 --> 00:16:05,360 Speaker 1: interrupt the current, so the field would dissipate, the springs 276 00:16:05,400 --> 00:16:08,120 Speaker 1: on the caliper would pull the caliper open again. It 277 00:16:08,200 --> 00:16:13,160 Speaker 1: was a very ingenious creation, but Sperry's invention didn't catch 278 00:16:13,280 --> 00:16:15,760 Speaker 1: on in the States. A similar idea would take off 279 00:16:15,760 --> 00:16:18,800 Speaker 1: in Europe, however, and I'll talk about a different breaking 280 00:16:18,800 --> 00:16:22,120 Speaker 1: system that would see early success in the United States, 281 00:16:22,400 --> 00:16:25,160 Speaker 1: and that early success would extend all the way into 282 00:16:25,280 --> 00:16:28,680 Speaker 1: the modern day. But I'll do that in just a second. First, 283 00:16:29,040 --> 00:16:39,960 Speaker 1: let's take a quick break. So right around the same 284 00:16:40,000 --> 00:16:44,760 Speaker 1: time Sperry was working on the disc brake solution, Gottlieb 285 00:16:44,920 --> 00:16:48,600 Speaker 1: Daimler was developing a different approach called the drum brake. 286 00:16:49,400 --> 00:16:52,240 Speaker 1: Daimler's idea was to attach a drum mounted on an 287 00:16:52,280 --> 00:16:56,320 Speaker 1: axle and to wrap a cable around that drum and 288 00:16:56,560 --> 00:17:00,120 Speaker 1: pulling the brake would create tension on the cable, tightening 289 00:17:00,200 --> 00:17:03,680 Speaker 1: it around the drum and creating the friction needed to 290 00:17:03,760 --> 00:17:06,880 Speaker 1: slow and then stop a vehicle. So if you can 291 00:17:06,960 --> 00:17:10,199 Speaker 1: think of maybe a spinning axle and then wrapping a 292 00:17:10,240 --> 00:17:13,320 Speaker 1: belt around it and then pulling the belt, really taught 293 00:17:13,520 --> 00:17:17,320 Speaker 1: so that that creates that friction and then slowing the 294 00:17:17,359 --> 00:17:19,840 Speaker 1: axle down. It's similar to that. So you have this 295 00:17:19,920 --> 00:17:23,359 Speaker 1: dedicated drum for this purpose. UH. This was an idea 296 00:17:23,480 --> 00:17:27,119 Speaker 1: that will Helm Maybach used in nineteen o one in 297 00:17:27,200 --> 00:17:31,160 Speaker 1: some early Mercedes designs, but it was Louis Renault who 298 00:17:31,280 --> 00:17:35,679 Speaker 1: defined the drum break as a standard in vehicles. It 299 00:17:35,760 --> 00:17:40,920 Speaker 1: was Renault's UH design that really took off. That being said, 300 00:17:41,119 --> 00:17:43,480 Speaker 1: there are also a ton of different mechanics and engineers 301 00:17:43,520 --> 00:17:45,800 Speaker 1: working on this problem, and so the idea may have 302 00:17:45,800 --> 00:17:50,199 Speaker 1: been developing in parallel around the world. Renault gets the 303 00:17:50,200 --> 00:17:53,600 Speaker 1: credit for making this the first really practical drum break, 304 00:17:54,480 --> 00:17:57,000 Speaker 1: but lots of people were working on this because the 305 00:17:57,000 --> 00:18:00,960 Speaker 1: automobile was a rising technology at the time. Now, the 306 00:18:01,080 --> 00:18:04,480 Speaker 1: drum brake is a pretty clever invention, and a modernized 307 00:18:04,600 --> 00:18:08,359 Speaker 1: version is still used in many vehicles today, though typically 308 00:18:08,400 --> 00:18:12,119 Speaker 1: only for the rear wheels for most passenger vehicles. It 309 00:18:12,240 --> 00:18:15,000 Speaker 1: was also the dominant form of breaking systems in the 310 00:18:15,080 --> 00:18:18,960 Speaker 1: United States until the nineteen seventies, though in Europe things 311 00:18:18,960 --> 00:18:23,080 Speaker 1: were a little different. The original drum brakes weren't great 312 00:18:23,400 --> 00:18:28,720 Speaker 1: on flat surfaces. These drum brakes that had a a 313 00:18:28,720 --> 00:18:32,679 Speaker 1: a belt or a strip of metal or something wrapped 314 00:18:32,720 --> 00:18:35,920 Speaker 1: around a drum that would then tighten to slow things down, 315 00:18:36,280 --> 00:18:39,439 Speaker 1: those worked fine on flat surfaces. A break race in 316 00:18:39,560 --> 00:18:43,440 Speaker 1: nineteen o two pitted a horse drawn coach that had 317 00:18:43,480 --> 00:18:49,200 Speaker 1: a lever style break against a Victoria horseless carriage that 318 00:18:49,280 --> 00:18:52,560 Speaker 1: had an internal drum brake, and a custom vehicle that 319 00:18:52,680 --> 00:18:55,879 Speaker 1: was created by a guy named Ransom E. Olds And 320 00:18:55,920 --> 00:19:01,200 Speaker 1: he called it the Oldsmobile. Yep, that's where that comes from. So, 321 00:19:01,600 --> 00:19:03,280 Speaker 1: like I said, the coach had a tire break, the 322 00:19:03,320 --> 00:19:06,240 Speaker 1: horseless carriage had an internal drum break, which I'll talk 323 00:19:06,240 --> 00:19:09,200 Speaker 1: about in a second, and the Oldsmobile had a different 324 00:19:09,280 --> 00:19:12,560 Speaker 1: drum brake design that used a band of stainless steel 325 00:19:13,200 --> 00:19:16,640 Speaker 1: wrapped around the drum. So pressing on the brake pedal 326 00:19:16,840 --> 00:19:20,840 Speaker 1: rather than pulling a lever would contract this band. So 327 00:19:20,880 --> 00:19:23,600 Speaker 1: that would grip the drum more tightly and thus create 328 00:19:23,680 --> 00:19:26,600 Speaker 1: the friction. The oldsmobile proved it could stop in less 329 00:19:26,640 --> 00:19:30,480 Speaker 1: time and thus travel the least distance while breaking than 330 00:19:30,520 --> 00:19:33,600 Speaker 1: the other two vehicles. So this meant that for a while, 331 00:19:33,880 --> 00:19:37,120 Speaker 1: external breaks, in which the breaking mechanism is on the 332 00:19:37,160 --> 00:19:41,480 Speaker 1: outside of the drum, were more popular, but both external 333 00:19:41,520 --> 00:19:44,680 Speaker 1: and internal drum breaking systems existed at the same time. 334 00:19:45,040 --> 00:19:49,239 Speaker 1: So what was an internal drum break system. Well, in 335 00:19:49,240 --> 00:19:52,720 Speaker 1: that case, you have the drum assembly that's mounted on 336 00:19:52,760 --> 00:19:55,960 Speaker 1: a wheel or an axle, So just think of it's 337 00:19:55,960 --> 00:19:59,760 Speaker 1: almost like a pot, right, It's just mounted on there 338 00:19:59,800 --> 00:20:03,760 Speaker 1: and and everything is inside this pot. So you have 339 00:20:03,840 --> 00:20:08,760 Speaker 1: these extendable parts inside the drum. They're called shoes. And 340 00:20:08,800 --> 00:20:12,800 Speaker 1: these extendable shoes are anchored with respect to the car, 341 00:20:12,880 --> 00:20:17,240 Speaker 1: so they are not rotating. They are stationary with respect 342 00:20:17,359 --> 00:20:20,960 Speaker 1: to the chassis of the vehicle. So the drum rotates 343 00:20:21,119 --> 00:20:26,639 Speaker 1: around these shoes as as the cars in motion. The 344 00:20:26,760 --> 00:20:30,840 Speaker 1: shoes have breaking material, so a material meant to generate 345 00:20:30,920 --> 00:20:36,680 Speaker 1: friction coding the surface of the shoe itself the stopping surface. 346 00:20:37,000 --> 00:20:39,399 Speaker 1: So when you engage the brake, when you step on 347 00:20:39,520 --> 00:20:44,199 Speaker 1: the brake, pedal A system extends these shoes on the 348 00:20:44,240 --> 00:20:47,760 Speaker 1: inside of the drum, so that that breaking surface is 349 00:20:47,880 --> 00:20:51,840 Speaker 1: rubbing up against the inside edge of that rotating drum. 350 00:20:52,160 --> 00:20:54,200 Speaker 1: So it's the same effect that you were getting before, 351 00:20:54,320 --> 00:20:58,760 Speaker 1: this idea of pressing a surface against a moving object 352 00:20:59,080 --> 00:21:02,560 Speaker 1: in order to generate friction and convert kinetic energy into heat. 353 00:21:02,800 --> 00:21:06,320 Speaker 1: It's just in this case it's happening on the inside 354 00:21:06,960 --> 00:21:11,040 Speaker 1: of a rotating surface, not on the outside of the 355 00:21:11,160 --> 00:21:16,760 Speaker 1: rotating surface. Uh. The this is really interesting stuff. It's 356 00:21:16,800 --> 00:21:20,639 Speaker 1: a little difficult to envision just from my audio, I imagine, 357 00:21:21,000 --> 00:21:23,919 Speaker 1: but if you really want to look into this and 358 00:21:23,960 --> 00:21:26,800 Speaker 1: see some diagrams and some animations and things like that, 359 00:21:27,200 --> 00:21:30,280 Speaker 1: How Stuff Works has several articles about breaks, including how 360 00:21:30,359 --> 00:21:33,520 Speaker 1: drum brakes work, and that's incredibly useful. So if you 361 00:21:33,560 --> 00:21:37,520 Speaker 1: want to check in on a visual aid, I highly 362 00:21:37,560 --> 00:21:40,760 Speaker 1: recommend that I don't write for How Stuff Works anymore, 363 00:21:41,080 --> 00:21:43,800 Speaker 1: but I still respect the heck out all the articles 364 00:21:43,800 --> 00:21:46,240 Speaker 1: that are on that site. They are incredibly useful, especially 365 00:21:46,400 --> 00:21:48,800 Speaker 1: for stuff like this, to get an understanding of these 366 00:21:48,840 --> 00:21:53,720 Speaker 1: mechanical systems. So in addition, uh, these brakes would typically 367 00:21:53,760 --> 00:21:57,240 Speaker 1: have some sort of cable or belt wrapped around the drum. 368 00:21:57,280 --> 00:21:59,240 Speaker 1: So you would have a lot of cars that would 369 00:21:59,280 --> 00:22:01,080 Speaker 1: have kind of a high red system where they have 370 00:22:01,160 --> 00:22:06,199 Speaker 1: both external and internal breaking UH systems incorporated into the 371 00:22:06,320 --> 00:22:12,840 Speaker 1: same overall brake system and create more friction more more efficiently, 372 00:22:13,000 --> 00:22:15,320 Speaker 1: so that you could convert that kinetic energy into heat 373 00:22:15,359 --> 00:22:19,359 Speaker 1: and stop faster. Now, early on, the external drum brake 374 00:22:19,480 --> 00:22:22,479 Speaker 1: systems were believed to be superior. They could stop a 375 00:22:22,480 --> 00:22:27,120 Speaker 1: car faster and less time less distance than internal ones, 376 00:22:27,200 --> 00:22:30,600 Speaker 1: but they did have some big drawbacks. One of those 377 00:22:30,680 --> 00:22:33,240 Speaker 1: was that the brakes would tend to unwind if you 378 00:22:33,320 --> 00:22:36,560 Speaker 1: try to stop halfway up a hill. So you you're driving, 379 00:22:37,040 --> 00:22:39,160 Speaker 1: you got a hill. Let's say you're in San Francisco. 380 00:22:39,200 --> 00:22:42,399 Speaker 1: That's a great example. You're in San Francisco, you hit 381 00:22:42,440 --> 00:22:44,760 Speaker 1: a hill, you're driving up the hill, and then you're 382 00:22:44,760 --> 00:22:48,080 Speaker 1: coming up to an intersection where you have to stop. Well, 383 00:22:49,160 --> 00:22:53,760 Speaker 1: that was an issue because the brakes would unwind. At 384 00:22:53,800 --> 00:22:56,720 Speaker 1: that point. Gravity would create a backward pull on the 385 00:22:56,760 --> 00:23:00,159 Speaker 1: car to pull it back down the hill, and that 386 00:23:00,160 --> 00:23:03,520 Speaker 1: would cause the bands wrapped around the drum to unwind 387 00:23:03,520 --> 00:23:06,320 Speaker 1: in the car would actually start to roll backwards. For 388 00:23:06,359 --> 00:23:11,360 Speaker 1: that reason, early motorists would sometimes carry wedged blocks called chalks, 389 00:23:12,080 --> 00:23:15,119 Speaker 1: just like you would have for an airplane, and you 390 00:23:15,160 --> 00:23:18,720 Speaker 1: would actually there's footage of people who were driving cars 391 00:23:18,760 --> 00:23:21,400 Speaker 1: around that time who would jump out of their car 392 00:23:21,560 --> 00:23:24,600 Speaker 1: with these wooden blocks, run behind the cars it's starting 393 00:23:24,640 --> 00:23:27,720 Speaker 1: to roll backward, and try to wedge those blocks behind 394 00:23:27,760 --> 00:23:31,200 Speaker 1: the wheels so that the car wasn't rolling backward anymore. 395 00:23:32,040 --> 00:23:35,080 Speaker 1: The external brakes also had no protection against dirt and 396 00:23:35,119 --> 00:23:37,440 Speaker 1: other debris, so they would get dirty and they would 397 00:23:37,440 --> 00:23:41,159 Speaker 1: wear down relatively quickly, which would necessitate frequent maintenance or 398 00:23:41,240 --> 00:23:45,640 Speaker 1: replacement of those brakes. The internal drum braking systems were 399 00:23:45,640 --> 00:23:48,920 Speaker 1: protected from debris and dirt right because they're inside the drum, 400 00:23:49,240 --> 00:23:53,200 Speaker 1: so that stuff wasn't getting to them. Although as you 401 00:23:53,359 --> 00:23:57,080 Speaker 1: use the drum brakes over and over over again, they 402 00:23:57,119 --> 00:24:02,840 Speaker 1: do develop dust inside the drum itself because it's actually 403 00:24:02,920 --> 00:24:07,439 Speaker 1: wearing away both the brake pads and the inside of 404 00:24:07,480 --> 00:24:11,160 Speaker 1: the drum. You know that friction is slowly grinding away 405 00:24:11,359 --> 00:24:14,719 Speaker 1: some of that material. But also because of the design, 406 00:24:15,160 --> 00:24:18,480 Speaker 1: the shoes inside a drum could maintain pressure for as 407 00:24:18,520 --> 00:24:21,280 Speaker 1: long as the brake was engaged, which meant there was 408 00:24:21,320 --> 00:24:23,560 Speaker 1: no need to worry about rolling backward down the hill. 409 00:24:23,600 --> 00:24:26,119 Speaker 1: If you had the brake pressed, then you know it 410 00:24:26,160 --> 00:24:29,399 Speaker 1: wasn't unwinding. If it was an internal drum brake, the 411 00:24:29,440 --> 00:24:33,000 Speaker 1: brakes would last longer than external breakes, but they weren't 412 00:24:33,040 --> 00:24:36,080 Speaker 1: as effective at stopping the vehicle as quickly, so for 413 00:24:36,119 --> 00:24:39,320 Speaker 1: that reason, some car manufacturers chose to employ both types 414 00:24:39,359 --> 00:24:42,119 Speaker 1: of brakes on the rear wheels of vehicles, in particular, 415 00:24:42,440 --> 00:24:45,560 Speaker 1: so that both an external and internal drum brake system 416 00:24:45,640 --> 00:24:48,879 Speaker 1: could work together from the same press of a brake pedal. 417 00:24:49,320 --> 00:24:53,080 Speaker 1: In those early systems, everything was purely mechanical. We haven't 418 00:24:53,080 --> 00:24:56,080 Speaker 1: gotten to the hydraulic sections yet, so that meant that 419 00:24:56,240 --> 00:24:59,880 Speaker 1: it was using stuff like cables and rods and levers 420 00:25:00,080 --> 00:25:04,440 Speaker 1: to do mechanical work and to move these different elements 421 00:25:05,080 --> 00:25:07,960 Speaker 1: to where they needed to be. Eventually that gave way 422 00:25:08,000 --> 00:25:11,439 Speaker 1: to hydraulic systems, but will have a different type of 423 00:25:11,480 --> 00:25:14,400 Speaker 1: break to talk about first before we get into hydraulics. 424 00:25:14,440 --> 00:25:16,720 Speaker 1: So that means we need to get back to Sperry's 425 00:25:16,920 --> 00:25:22,520 Speaker 1: disc brakes. His implementation didn't get much traction, and yes 426 00:25:22,560 --> 00:25:27,280 Speaker 1: that's a pun, but others began to work on similar designs, 427 00:25:27,320 --> 00:25:31,160 Speaker 1: possibly with complete independence and without knowledge of Sperry's work, because, 428 00:25:31,160 --> 00:25:32,679 Speaker 1: like I said, a lot of people were working on 429 00:25:32,720 --> 00:25:36,320 Speaker 1: this at the same time. Uh. One of those was 430 00:25:36,359 --> 00:25:39,960 Speaker 1: an inventor named F. W. Lanchester in the UK who 431 00:25:39,960 --> 00:25:42,720 Speaker 1: received a patent in nineteen o two for a mechanical 432 00:25:42,760 --> 00:25:46,400 Speaker 1: approach to the disc brake design, so instead of the 433 00:25:46,480 --> 00:25:51,200 Speaker 1: electromagnetic approach, the calipers would be controlled by a cable. 434 00:25:52,080 --> 00:25:55,480 Speaker 1: The cable, when pulled taught, would force the calipers closed. 435 00:25:55,840 --> 00:25:59,960 Speaker 1: But lanchester solution wasn't ideal. The disc mounted to the 436 00:26:00,000 --> 00:26:02,840 Speaker 1: wheel hub was made of metal, which makes sense, but 437 00:26:02,920 --> 00:26:05,800 Speaker 1: the brake pads that were actually on the caliper were 438 00:26:05,840 --> 00:26:09,200 Speaker 1: made out of copper, So when you were applying a break, 439 00:26:09,440 --> 00:26:12,280 Speaker 1: that meant that you were applying to copper pads on 440 00:26:12,320 --> 00:26:15,760 Speaker 1: either side of a rapidly spinning metal disc. And as 441 00:26:15,800 --> 00:26:20,000 Speaker 1: you might imagine, this created no small amount of noise. 442 00:26:20,840 --> 00:26:23,520 Speaker 1: From what I understand, it was the type of high pitched, 443 00:26:23,640 --> 00:26:26,639 Speaker 1: screeching noise that was not that different from what you 444 00:26:26,720 --> 00:26:30,480 Speaker 1: might get with fingernails dragged down a chalkboard, so not 445 00:26:30,600 --> 00:26:33,960 Speaker 1: a pleasant sound. In addition, the brake pads would wear 446 00:26:34,000 --> 00:26:36,520 Speaker 1: down very quickly and had the same issues with dart 447 00:26:36,560 --> 00:26:40,000 Speaker 1: and debris that the external drum systems had, so lanchester 448 00:26:40,119 --> 00:26:45,720 Speaker 1: solution was, like Sperry's, largely unimplemented. A dude named Fruit 449 00:26:46,320 --> 00:26:50,000 Speaker 1: made the next big contribution. His name is Herbert Fruit. 450 00:26:50,320 --> 00:26:53,160 Speaker 1: He was an English engineer who took the brake pads 451 00:26:53,480 --> 00:26:55,720 Speaker 1: and lined them with a substance that would cut back 452 00:26:55,760 --> 00:26:59,159 Speaker 1: on that noise. It was a long lasting material that 453 00:26:59,160 --> 00:27:02,240 Speaker 1: could withstand a lot of abuse, and it would become 454 00:27:02,320 --> 00:27:05,320 Speaker 1: a common brake pad material for both disc brakes and 455 00:27:05,400 --> 00:27:08,000 Speaker 1: drum brakes, and still is used in a lot of 456 00:27:08,040 --> 00:27:15,480 Speaker 1: breaks today. That material was asbestos. Yikes, So asbestos was 457 00:27:15,560 --> 00:27:19,639 Speaker 1: long considered a truly remarkable substance with a ton of 458 00:27:19,680 --> 00:27:23,960 Speaker 1: practical applications. It's actually a group of silicate minerals, it's 459 00:27:24,000 --> 00:27:28,280 Speaker 1: not just one, and this group all have similar traits 460 00:27:28,280 --> 00:27:31,200 Speaker 1: their fibrous which means you can actually draw the stuff 461 00:27:31,240 --> 00:27:34,600 Speaker 1: out and create a material that's similar in consistency to 462 00:27:35,160 --> 00:27:38,600 Speaker 1: cotton balls in a way. Its heat resistant, it's an 463 00:27:38,600 --> 00:27:41,639 Speaker 1: electrical insulator, and it holds up against a lot of 464 00:27:41,680 --> 00:27:45,760 Speaker 1: otherwise corrosive chemicals, so it can make other stuff stronger 465 00:27:45,880 --> 00:27:48,080 Speaker 1: when you mix the substances together, and it was a 466 00:27:48,080 --> 00:27:52,520 Speaker 1: common additive for everything from cement to paper. But what 467 00:27:52,800 --> 00:27:55,720 Speaker 1: was not known for a very long time was that 468 00:27:55,800 --> 00:28:01,280 Speaker 1: asbestos is actually incredibly toxic. Now, as I said, it's fibrous, 469 00:28:01,480 --> 00:28:04,159 Speaker 1: and so they are these tiny asbestos fibers in the 470 00:28:04,200 --> 00:28:08,600 Speaker 1: mineral and these can easily be swallowed or inhaled without 471 00:28:08,600 --> 00:28:11,840 Speaker 1: your knowledge. Their microscopic in size, so you're not able 472 00:28:11,880 --> 00:28:15,000 Speaker 1: to spot them. And due to those qualities I mentioned earlier, 473 00:28:15,119 --> 00:28:17,840 Speaker 1: the fact that the fibers are so resistant to so 474 00:28:17,920 --> 00:28:21,280 Speaker 1: many different things, it also means that they can last 475 00:28:21,400 --> 00:28:24,680 Speaker 1: indefinitely inside a person's body and there's no real way 476 00:28:24,720 --> 00:28:28,240 Speaker 1: to flush them out. They don't dissolve, and these trapped 477 00:28:28,280 --> 00:28:32,800 Speaker 1: fibers can cause inflammation and even much worse problems genetic 478 00:28:32,880 --> 00:28:37,920 Speaker 1: damage to cells. Uh they can lead to development of cancer. 479 00:28:38,320 --> 00:28:41,440 Speaker 1: The illnesses take a really long time to develop, too, 480 00:28:41,600 --> 00:28:44,520 Speaker 1: like between twenty to fifty years, which is one of 481 00:28:44,560 --> 00:28:47,480 Speaker 1: the reasons asbestos remained in popular use for so long. 482 00:28:47,520 --> 00:28:50,440 Speaker 1: It took ages to figure out that it was hazardous 483 00:28:50,440 --> 00:28:53,880 Speaker 1: in the first place because the effects took so long 484 00:28:54,200 --> 00:28:58,520 Speaker 1: to manifest. Now, nearly all the auto manufacturers in the 485 00:28:58,560 --> 00:29:02,800 Speaker 1: United States stopped making asbestos brake pads in the ninety nineties, 486 00:29:03,200 --> 00:29:06,280 Speaker 1: but there are a lot of aftermarket companies that continue 487 00:29:06,320 --> 00:29:09,479 Speaker 1: to do so, largely manufacturing in places like China and 488 00:29:09,560 --> 00:29:14,200 Speaker 1: India and Mexico. So to this day, there are aftermarket 489 00:29:14,280 --> 00:29:19,440 Speaker 1: brake pads that have potentially dangerous amounts of asbestos in them. Now, 490 00:29:19,480 --> 00:29:23,280 Speaker 1: that probably doesn't pose a huge health hazard to the 491 00:29:23,320 --> 00:29:27,640 Speaker 1: average driver, but it is a concern for mechanics. For 492 00:29:27,720 --> 00:29:31,360 Speaker 1: people who work on break systems regularly, that's something that 493 00:29:31,400 --> 00:29:35,640 Speaker 1: they should actively be concerned about and protect themselves against. 494 00:29:35,680 --> 00:29:40,200 Speaker 1: Because there's no telling if someone's getting cheap break pads 495 00:29:40,240 --> 00:29:43,720 Speaker 1: from overseas, because you know there they are much less 496 00:29:43,720 --> 00:29:47,600 Speaker 1: expensive than buying them here Domestically, there's a chance that 497 00:29:47,680 --> 00:29:50,320 Speaker 1: one of the materials in there is asbestos and it 498 00:29:50,360 --> 00:29:52,440 Speaker 1: could be in a concentration high enough for it to 499 00:29:52,440 --> 00:29:55,480 Speaker 1: be a danger. So just to be aware if you 500 00:29:55,560 --> 00:29:58,000 Speaker 1: happen to be someone who works on such things, just 501 00:29:58,320 --> 00:30:00,640 Speaker 1: you know, you need to just be care full. We're 502 00:30:01,040 --> 00:30:03,480 Speaker 1: masks and stuff. Now. I've got a lot more to 503 00:30:03,520 --> 00:30:06,800 Speaker 1: say about breaks, including the introduction of hydraulics and modern 504 00:30:06,880 --> 00:30:18,360 Speaker 1: breaking systems, but first let's take another quick break. Now, 505 00:30:18,360 --> 00:30:21,520 Speaker 1: it didn't take long for engineers to look into hydraulics 506 00:30:21,560 --> 00:30:24,840 Speaker 1: to work with car brakes. Cars were getting heavier and faster, 507 00:30:24,960 --> 00:30:27,120 Speaker 1: which meant the brake systems needed to be up to 508 00:30:27,240 --> 00:30:30,800 Speaker 1: the task of bringing these increasingly speedy hunks of metal 509 00:30:30,880 --> 00:30:35,680 Speaker 1: to a stop. In nineteen eighteen, Malcolm Lockheed actually law 510 00:30:35,760 --> 00:30:39,960 Speaker 1: feed at the time, began to experiment with hydraulics. So 511 00:30:40,200 --> 00:30:44,000 Speaker 1: what exactly is a hydraulic system and why is it important? Well, 512 00:30:44,120 --> 00:30:47,960 Speaker 1: hydraulics is a branch of science that is really about 513 00:30:48,000 --> 00:30:54,080 Speaker 1: the practical applications of fluids, typically liquids. It's largely, but 514 00:30:54,160 --> 00:30:59,280 Speaker 1: not exclusively, about how those fluids moved through systems like pipes, channels, 515 00:30:59,320 --> 00:31:04,280 Speaker 1: and tanks. Blaze Pascal and Daniel Bernoulli first worked out 516 00:31:04,280 --> 00:31:07,880 Speaker 1: the basic principles of fluid dynamics and hydraulic power. But 517 00:31:08,000 --> 00:31:10,800 Speaker 1: people had been making practical use of fluids for some 518 00:31:10,880 --> 00:31:13,280 Speaker 1: time already, So this was one of those things where 519 00:31:13,320 --> 00:31:16,520 Speaker 1: people had figured out that they could could use fluids 520 00:31:16,560 --> 00:31:19,120 Speaker 1: to do work, but no one had quite worked out 521 00:31:19,160 --> 00:31:22,960 Speaker 1: the science behind it yet until Pascal and Bernoulli came along. 522 00:31:23,240 --> 00:31:26,920 Speaker 1: Pascal figured out that a pressure in an incompressible liquid 523 00:31:27,200 --> 00:31:30,840 Speaker 1: transmits equally in all directions, and this law ends up 524 00:31:30,840 --> 00:31:33,640 Speaker 1: being incredibly useful if you want to leverage fluids to 525 00:31:33,720 --> 00:31:36,520 Speaker 1: do work. Bernoulli's last data that energy and a fluid 526 00:31:36,560 --> 00:31:40,320 Speaker 1: remains constant, but that changing things like the diameter of 527 00:31:40,320 --> 00:31:43,840 Speaker 1: a pipe will change the pressure in a system. The 528 00:31:43,960 --> 00:31:46,640 Speaker 1: energy remains the same, but the flow slows down as 529 00:31:46,640 --> 00:31:48,880 Speaker 1: it encounters a larger diameter, and the surface area of 530 00:31:48,920 --> 00:31:52,800 Speaker 1: the fluid presses against is increased. And effectively, what that 531 00:31:52,840 --> 00:31:56,960 Speaker 1: means is you can create mechanical advantage through hydraulic systems. 532 00:31:57,000 --> 00:32:00,880 Speaker 1: So if we have a closed system with income rescible fluid, 533 00:32:01,040 --> 00:32:03,240 Speaker 1: so you if you push against the fluid, you can't 534 00:32:03,280 --> 00:32:06,280 Speaker 1: compress it to a smaller form. It's going to push 535 00:32:06,320 --> 00:32:11,680 Speaker 1: against all areas equally. We can actually transfer force from 536 00:32:11,720 --> 00:32:14,600 Speaker 1: one side of a system to another, with the liquid 537 00:32:14,640 --> 00:32:17,920 Speaker 1: acting as the carrier for that force. And by changing 538 00:32:17,960 --> 00:32:22,920 Speaker 1: the sizes of cylinders and pistons, you can also amplify 539 00:32:23,200 --> 00:32:27,440 Speaker 1: force by trading force for distance, kind of similar to 540 00:32:27,480 --> 00:32:29,800 Speaker 1: what we were doing when we were talking about levers. 541 00:32:29,880 --> 00:32:32,920 Speaker 1: So let's say we've got two pistons connected in a 542 00:32:33,000 --> 00:32:36,480 Speaker 1: hydraulic system. It's much easier to understand if we take 543 00:32:36,560 --> 00:32:40,000 Speaker 1: a concrete example, or at least a hypothetical example. So 544 00:32:40,800 --> 00:32:44,720 Speaker 1: we've got piston one. Piston one is two inches in 545 00:32:44,760 --> 00:32:48,440 Speaker 1: diameter or one inch radius. That's a five point eight 546 00:32:48,840 --> 00:32:53,040 Speaker 1: centimeters in diameter. Piston two is six inches in diameter 547 00:32:53,200 --> 00:32:57,800 Speaker 1: or fifteen point to four centimeters in diameter. So then 548 00:32:57,840 --> 00:32:59,800 Speaker 1: we have to figure out the area of these two 549 00:32:59,800 --> 00:33:03,920 Speaker 1: p stance and area of a circle is pie times 550 00:33:03,920 --> 00:33:07,960 Speaker 1: the radius squared, So piston one has the radius of 551 00:33:08,000 --> 00:33:11,560 Speaker 1: one inch. One inch squared is one one times pie 552 00:33:11,720 --> 00:33:15,040 Speaker 1: is three point one four, etcetera, etcetera. So we just 553 00:33:15,160 --> 00:33:17,680 Speaker 1: will simplify to say three point one four is the 554 00:33:17,760 --> 00:33:21,840 Speaker 1: area of our first piston. Our second piston has an 555 00:33:21,880 --> 00:33:29,280 Speaker 1: area of twenty eight point two six because it's much larger. 556 00:33:29,360 --> 00:33:33,200 Speaker 1: So that means piston two is nine times the size 557 00:33:33,200 --> 00:33:36,760 Speaker 1: of piston one in area. If we apply a force 558 00:33:36,840 --> 00:33:39,719 Speaker 1: to piston one in this closed system where we have 559 00:33:39,800 --> 00:33:45,360 Speaker 1: liquid acting as the uh the transmission force between one 560 00:33:45,440 --> 00:33:49,440 Speaker 1: piston and the other. So we push a piston one down, 561 00:33:49,520 --> 00:33:53,000 Speaker 1: we're gonna get nine times that force on piston two. 562 00:33:53,520 --> 00:33:55,920 Speaker 1: So if we push down on piston one with one 563 00:33:56,320 --> 00:34:00,480 Speaker 1: pounds of force, it makes piston two go up. Nine 564 00:34:00,560 --> 00:34:03,800 Speaker 1: hundred pounds of force because piston two is nine times 565 00:34:03,840 --> 00:34:06,040 Speaker 1: the size of piston one. However, there is a tradeoff. 566 00:34:06,680 --> 00:34:10,480 Speaker 1: That tradeoff is in the distance traveled by the each piston. 567 00:34:11,160 --> 00:34:15,399 Speaker 1: Piston two will travel one ninth the distance of piston one. 568 00:34:15,880 --> 00:34:18,879 Speaker 1: So in order to make piston two rise up one inch, 569 00:34:19,239 --> 00:34:22,640 Speaker 1: you would have to push piston one down nine inches 570 00:34:23,640 --> 00:34:26,799 Speaker 1: push down piston one nine inches into a cylinder at 571 00:34:26,840 --> 00:34:29,839 Speaker 1: one dred pounds of pressure. Piston two will lift up 572 00:34:30,040 --> 00:34:34,000 Speaker 1: one inch with nine hundred pounds of pressure, so you 573 00:34:34,040 --> 00:34:38,520 Speaker 1: amplify the force you decrease the distance. Lackeed's method, in 574 00:34:38,520 --> 00:34:41,200 Speaker 1: which hydraulic pressure would create the force that would push 575 00:34:41,239 --> 00:34:46,440 Speaker 1: a brake shoe against the brake drums, wasn't embraced immediately. 576 00:34:46,640 --> 00:34:50,120 Speaker 1: According to Popular Mechanics, the first passenger car to have 577 00:34:50,320 --> 00:34:54,640 Speaker 1: four wheel hydraulic brakes was the Model A Dusenberg in 578 00:34:54,760 --> 00:34:58,200 Speaker 1: nineteen twenty one. A decade later, a handful of car 579 00:34:58,239 --> 00:35:01,400 Speaker 1: manufacturers were using hydraulics and the brake systems, but the 580 00:35:01,440 --> 00:35:04,480 Speaker 1: rest were still relying on cable brakes. Ford would be 581 00:35:04,520 --> 00:35:07,160 Speaker 1: the last of the major manufacturers to make the switch 582 00:35:07,200 --> 00:35:12,080 Speaker 1: to hydraulics, and that happened in nineteen thirty nine. Going 583 00:35:12,080 --> 00:35:14,839 Speaker 1: back just a bit in n another advance helped make 584 00:35:14,880 --> 00:35:20,200 Speaker 1: hydraulic disc brakes practical. It was the power assist technology, 585 00:35:20,239 --> 00:35:23,000 Speaker 1: and that would reduce the physical effort a driver would 586 00:35:23,040 --> 00:35:25,840 Speaker 1: have to exert to apply the brakes. So if you 587 00:35:25,880 --> 00:35:28,600 Speaker 1: didn't have power assist, you would find that you have 588 00:35:28,680 --> 00:35:31,960 Speaker 1: to push that brake pedal really hard in order to stop. 589 00:35:32,560 --> 00:35:34,840 Speaker 1: So instead of having to really stomp on the brake pedal, 590 00:35:35,640 --> 00:35:37,959 Speaker 1: the driver just uses a little effort and the car 591 00:35:38,120 --> 00:35:41,880 Speaker 1: itself would help to do the rest. The N Pierce 592 00:35:42,040 --> 00:35:45,400 Speaker 1: arrow used vacuum that was generated by the inlet manifold 593 00:35:45,480 --> 00:35:48,040 Speaker 1: of the engine to offset the physical force required by 594 00:35:48,040 --> 00:35:51,640 Speaker 1: the driver. Diesel powered cars, by the way, actually require 595 00:35:51,680 --> 00:35:54,960 Speaker 1: a secondary vacuum pump to generate the vacuum necessary for 596 00:35:54,960 --> 00:35:57,279 Speaker 1: the power assiste because their engines don't work the same 597 00:35:57,280 --> 00:36:00,440 Speaker 1: way anyway. Describing how all this works is tri key 598 00:36:00,480 --> 00:36:04,680 Speaker 1: without using visual aids. It involves a diaphragm that initially 599 00:36:04,680 --> 00:36:08,200 Speaker 1: has a partial vacuum on either side of the diaphragm, 600 00:36:08,239 --> 00:36:10,279 Speaker 1: but when you press the brake pedal, it opens up 601 00:36:10,280 --> 00:36:13,840 Speaker 1: a valve on the vacuum booster side. Of the diaphragm 602 00:36:13,880 --> 00:36:16,760 Speaker 1: and increases the pressure on that side and thus gives 603 00:36:16,840 --> 00:36:19,439 Speaker 1: the boost to the driver who's pushing down on the brake. 604 00:36:20,120 --> 00:36:22,760 Speaker 1: To understand this, I really recommend looking at the article 605 00:36:22,840 --> 00:36:25,280 Speaker 1: how power brakes work on the House Stuff Works site, 606 00:36:25,719 --> 00:36:29,080 Speaker 1: because like I said, it's really hard to describe just 607 00:36:29,160 --> 00:36:32,640 Speaker 1: in audio alone and haven't make any sense. But the 608 00:36:32,680 --> 00:36:36,000 Speaker 1: point is this was one of those necessary features to 609 00:36:36,080 --> 00:36:40,520 Speaker 1: make hydraulic brakes practical to remove some of that effort 610 00:36:40,560 --> 00:36:43,239 Speaker 1: that was required in order to push down on the brake. 611 00:36:43,840 --> 00:36:46,000 Speaker 1: Oh and and hey, remember when I talked about the 612 00:36:46,080 --> 00:36:48,040 Speaker 1: lever at the top of the episode and how the 613 00:36:48,080 --> 00:36:50,200 Speaker 1: distances between a force of fulcrum and a load can 614 00:36:50,200 --> 00:36:52,480 Speaker 1: affect how much force you apply on the system. The 615 00:36:52,520 --> 00:36:55,640 Speaker 1: same is true with brake pedals. Brake pedals are actually levers, 616 00:36:55,640 --> 00:36:59,440 Speaker 1: their class two levers, so the distance the pedal has 617 00:36:59,480 --> 00:37:02,520 Speaker 1: to travel tends to be much greater than the distance 618 00:37:02,600 --> 00:37:06,480 Speaker 1: from the pedal cylinder to the pivot, so the force 619 00:37:06,560 --> 00:37:09,040 Speaker 1: of the pedal will be multiplied at the point of 620 00:37:09,040 --> 00:37:12,000 Speaker 1: the cylinder. So these are all both These are all 621 00:37:12,000 --> 00:37:15,760 Speaker 1: like mechanical ways to make it easier to actually apply 622 00:37:15,800 --> 00:37:20,560 Speaker 1: the brakes physically easier. Typically, a hydraulic brake system has 623 00:37:20,640 --> 00:37:23,920 Speaker 1: one master cylinder, so this is the one that's actually 624 00:37:23,960 --> 00:37:27,560 Speaker 1: controlled by your brake pedal. The pedal cylinder with a 625 00:37:27,600 --> 00:37:30,720 Speaker 1: piston that connects via a rod to the brake pedal, 626 00:37:31,200 --> 00:37:33,360 Speaker 1: so it's like a direct line from the brake pedal 627 00:37:33,480 --> 00:37:38,480 Speaker 1: through a rod to the the actual piston for the 628 00:37:38,520 --> 00:37:43,640 Speaker 1: master cylinder. There's usually some more complicated stuff in there now, 629 00:37:43,719 --> 00:37:46,360 Speaker 1: especially for modern vehicles, but this is the basic idea. 630 00:37:47,040 --> 00:37:49,960 Speaker 1: Each wheel on a car tends to have its own 631 00:37:50,000 --> 00:37:54,080 Speaker 1: secondary cylinder, sometimes called a slave cylinder, the master cylinder 632 00:37:54,080 --> 00:37:57,480 Speaker 1: and the slave cylinders. The master cylinder tends to be 633 00:37:57,600 --> 00:38:00,799 Speaker 1: smaller than the slave cylinders, so we get that force 634 00:38:00,840 --> 00:38:04,080 Speaker 1: amplification effect I just talked about. This is what allows 635 00:38:04,120 --> 00:38:06,640 Speaker 1: the brakes to apply enough force to slow down a 636 00:38:06,760 --> 00:38:10,680 Speaker 1: massive vehicle traveling at high speeds, just from a human 637 00:38:10,760 --> 00:38:14,320 Speaker 1: stepping down on a brake pedal. Alright, so we've covered 638 00:38:14,360 --> 00:38:16,759 Speaker 1: drum brakes, which you can still find on many car 639 00:38:16,840 --> 00:38:20,240 Speaker 1: models on the rear wheels, and we've covered disc brakes, 640 00:38:20,320 --> 00:38:23,480 Speaker 1: which were adopted quickly in Europe and later in America 641 00:38:23,560 --> 00:38:26,080 Speaker 1: and tend to be the brake system used for front wheels. 642 00:38:26,800 --> 00:38:30,359 Speaker 1: Both systems now rely on hydraulics to transmit force from 643 00:38:30,400 --> 00:38:33,520 Speaker 1: the brake pedal to the brakes attached to the respective 644 00:38:33,520 --> 00:38:37,960 Speaker 1: wheels to those those UH brake shoes or the brake calipers. 645 00:38:38,600 --> 00:38:41,160 Speaker 1: There's also the emergency brake, which may have a physical 646 00:38:41,280 --> 00:38:45,359 Speaker 1: cable attached to a brake shoe UH that in turn 647 00:38:45,440 --> 00:38:49,239 Speaker 1: is attached to one or more wheels. And there's one 648 00:38:49,320 --> 00:38:51,520 Speaker 1: other advance I feel like I should cover, and that's 649 00:38:51,600 --> 00:38:54,799 Speaker 1: anti lock braking systems or a B s. What are 650 00:38:54,840 --> 00:38:58,240 Speaker 1: they and how do they work well? A skidding wheel 651 00:38:58,600 --> 00:39:02,080 Speaker 1: has less traction and a non skidding wheel, and a 652 00:39:02,160 --> 00:39:04,920 Speaker 1: skidding wheel is one in which the patch of tire 653 00:39:05,080 --> 00:39:08,560 Speaker 1: in contact with the road is sliding relative to that 654 00:39:08,640 --> 00:39:11,560 Speaker 1: road and the wheel the tire itself is not rotating anymore. 655 00:39:11,560 --> 00:39:14,680 Speaker 1: It's locked. So if you can break a car without 656 00:39:14,960 --> 00:39:18,560 Speaker 1: locking the tire, like without locking the wheels down entirely, 657 00:39:18,880 --> 00:39:21,760 Speaker 1: but rather applying pressure so that the wheels are slowed 658 00:39:21,800 --> 00:39:24,720 Speaker 1: to a stop, you're in better shape. You're not gonna 659 00:39:24,920 --> 00:39:27,680 Speaker 1: skid out and have a terrible accident, or at least 660 00:39:27,680 --> 00:39:29,279 Speaker 1: you won't have a terrible accident in that way. This 661 00:39:29,360 --> 00:39:32,640 Speaker 1: is particularly important on slippery road conditions, and that's what 662 00:39:32,760 --> 00:39:35,319 Speaker 1: a b S or anti lock brake systems do so. 663 00:39:35,400 --> 00:39:39,200 Speaker 1: And a b S has four main additional components on 664 00:39:39,360 --> 00:39:43,280 Speaker 1: top of the regular brake system. You have speed sensors 665 00:39:43,320 --> 00:39:46,640 Speaker 1: that's what's monitoring the speed of rotation of the wheels. 666 00:39:47,360 --> 00:39:50,799 Speaker 1: You have a set of valves, you have pump, and 667 00:39:50,840 --> 00:39:54,759 Speaker 1: you have a controller. The sensors are pretty self explanatory, 668 00:39:54,840 --> 00:39:56,400 Speaker 1: Like I said, they monitor the wheels. They live for 669 00:39:56,480 --> 00:39:58,640 Speaker 1: signs that the wheel is about to lock into position, 670 00:39:59,480 --> 00:40:03,480 Speaker 1: which means the wheel would actually stop spinning entirely. The 671 00:40:03,719 --> 00:40:06,920 Speaker 1: sensors may be located at each wheel, or it might 672 00:40:06,920 --> 00:40:10,400 Speaker 1: be located at the differential. The valves are meant to 673 00:40:10,440 --> 00:40:14,239 Speaker 1: control break pressure from the master cylinder, so the master 674 00:40:14,320 --> 00:40:17,360 Speaker 1: cylinders providing the pressure for the overall brake system. A 675 00:40:17,440 --> 00:40:21,080 Speaker 1: valve can be open and thus send pressure onto the 676 00:40:21,120 --> 00:40:23,480 Speaker 1: brake system as per normal. So in other words, it's 677 00:40:23,560 --> 00:40:25,319 Speaker 1: it's almost as if the valve is not even there. 678 00:40:26,040 --> 00:40:30,200 Speaker 1: It could be closed and block the hydraulics from going 679 00:40:30,239 --> 00:40:33,239 Speaker 1: to the break from the master cylinder. This would be 680 00:40:33,280 --> 00:40:36,560 Speaker 1: for each individual wheel would have its own so it's 681 00:40:36,560 --> 00:40:39,000 Speaker 1: not like one for all four wheels. It's one for 682 00:40:39,080 --> 00:40:42,040 Speaker 1: each wheel, so in that case, the hydraulic fluid would 683 00:40:42,120 --> 00:40:45,600 Speaker 1: essentially bypass that wheels brake system, and then the valve 684 00:40:45,640 --> 00:40:48,760 Speaker 1: has a third position to release some of the pressure 685 00:40:48,920 --> 00:40:52,120 Speaker 1: from the brake system. Now, because there's a pressure release system, 686 00:40:52,239 --> 00:40:55,360 Speaker 1: the a B S needs a pump to build pressure 687 00:40:55,440 --> 00:40:58,640 Speaker 1: up again, and the controller is essentially the brains, it's 688 00:40:58,640 --> 00:41:01,520 Speaker 1: in charge of the whole thing. The controller sends signals 689 00:41:01,520 --> 00:41:05,279 Speaker 1: to decrease or increase break pressure to individual wheels to 690 00:41:05,360 --> 00:41:09,160 Speaker 1: avoid lock up, while still allowing for deceleration. The hydraulic 691 00:41:09,200 --> 00:41:11,920 Speaker 1: system begins to pulse a bit as this happens, which 692 00:41:12,000 --> 00:41:15,040 Speaker 1: can feel a little weird if you if you're not 693 00:41:15,200 --> 00:41:18,280 Speaker 1: used to it, and those that pulse can be fast. 694 00:41:18,320 --> 00:41:20,960 Speaker 1: It can be like fifteen times per second with some vehicles. 695 00:41:21,880 --> 00:41:27,279 Speaker 1: A BS doesn't magically make cars safer in all conditions, 696 00:41:27,320 --> 00:41:29,239 Speaker 1: but they do come in really handy, as I said, 697 00:41:29,239 --> 00:41:31,560 Speaker 1: in those slippery road conditions, so they do have a 698 00:41:31,600 --> 00:41:35,200 Speaker 1: real benefit. But that does not mean that a BS 699 00:41:35,320 --> 00:41:38,080 Speaker 1: is magically going to make every driver safer. There are 700 00:41:38,160 --> 00:41:42,360 Speaker 1: possible problems that you can encounter. So, for one example, 701 00:41:43,000 --> 00:41:45,640 Speaker 1: when you're breaking with a system that doesn't have anti 702 00:41:45,680 --> 00:41:49,880 Speaker 1: lock brakes, you can't steer while you're breaking. Steering is 703 00:41:49,920 --> 00:41:52,919 Speaker 1: locked with a b S, you can still steer while 704 00:41:52,960 --> 00:41:55,799 Speaker 1: you're breaking, and sometimes that I can actually lead to 705 00:41:56,040 --> 00:42:00,279 Speaker 1: drivers making bad decisions and steering off the road. There's 706 00:42:00,320 --> 00:42:03,480 Speaker 1: a lot more that we could say about break systems 707 00:42:03,640 --> 00:42:06,960 Speaker 1: and newer innovations in the space. Uh there are some 708 00:42:07,040 --> 00:42:08,920 Speaker 1: high tech things that we can cover, but I think 709 00:42:08,920 --> 00:42:11,799 Speaker 1: I'm going to save that for another episode. We'll we'll 710 00:42:11,920 --> 00:42:15,239 Speaker 1: talk more in detail about some cutting edge materials and 711 00:42:16,040 --> 00:42:19,279 Speaker 1: techniques and breaking sometime down the line, but for now, 712 00:42:19,360 --> 00:42:22,040 Speaker 1: let's put us stop to this. If you guys have 713 00:42:22,120 --> 00:42:25,160 Speaker 1: suggestions for future topics for tech stuff, why not write 714 00:42:25,200 --> 00:42:27,840 Speaker 1: me and let me know The email addresses tech stuff 715 00:42:28,200 --> 00:42:31,879 Speaker 1: at how stuff works dot com or pop on by 716 00:42:31,960 --> 00:42:34,560 Speaker 1: our website. The u r L for that is text 717 00:42:34,600 --> 00:42:38,319 Speaker 1: stuff podcast dot com. You'll find links there to our 718 00:42:38,480 --> 00:42:41,920 Speaker 1: social media as well as to the merchandise store. Remember 719 00:42:42,040 --> 00:42:44,560 Speaker 1: every purchase you make goes to help the show, and 720 00:42:44,600 --> 00:42:47,640 Speaker 1: we greatly appreciate it. And I'll talk to you again 721 00:42:48,400 --> 00:42:56,840 Speaker 1: really soon for more on this and bathans of other topics. 722 00:42:56,880 --> 00:43:04,080 Speaker 1: Because it how staff works dot com really really wonder